Non-binding norms have become increasingly popular in the law of outer space. After the 1979 Moon Agreement, no further international treaty has been adopted. Instead, a number of non-binding instruments, has been produced. This book analyzes to what extent such "soft law" - even if the term is sometimes criticized - fulfills its function and has in fact an influence on States and private actors in their conduct of space activities. The authors are academics and practitioners and discuss, after a general theoretical introduction, the different instruments in the fields of space debris, nuclear power sources, remote sensing, registration practice, liability, and demilitarization.